A serving is the amount of food recommended in consumer education materials such as MyPlate. A portion is the amount of a food you choose to eat at any one time â which may be more or less than a serving. Here are some everyday comparisons to help you figure out your serving sizes. 1  1 teaspoon of margarine is the size of one dice. 2  3 ounces of meat is the size of a deck of cards. 3  1 cup of pasta is the size of a baseball. 4  1Â½ ounces of cheese is the size of four stacked dice.
1 If the oxygen concentration in the blood decreases, they tell the respiratory centers to increase the rate and depth of breathing.  Carbon dioxide: Peripheral chemoreceptors also monitor the carbon dioxide concentration in the blood.
Direct chemoreceptors are also found in the carotid body, a structure located at the branch of the carotid artery. These nerves detect levels of oxygen and carbon dioxide in the blood to determine when someone needs to breathe.hemoreceptors are specialized nerve cells which are designed to respond to chemical stimuli. The body contains both direct and distant chemoreceptors, all of which play important roles in bodily function and daily life.